Master cylender leak?

[XS1100_OEM4ME]

OK, I "had" a brand new in the box OEM complet master cyl and decided to sell it on Ebay as mine worked fine A few weeks after I sold it, mine started leaking from the plunger input shaft Murphy's Law, right. So I took it apart and cleaned it well, took super fine scotchbright and shined it like chrome inside, put it back togather with the old plungers, and it leaked Took it back apart, cleaned again, checked for scuffs, bought a new rebuild kit, put it back togather, and it is leaking, same place I used top of the line synthetic Dot 3&4 grade fluid and blead both front calipers, any thoughts. I have done thousands or break jobs on cars and some bikes, rebuilt calipers, wheel cyl's master cyls, did it for a living for years, I am starting to beleive this bike is cursed

[Cobia]

I think your problem may be the synthetic fluid. These bikes ONLY like DOT 3, not four, and the old type not the synth. Has something to do with how the rubber components react to it.
You may want to take it out again, clean it, drain the system, fill with regular DOT 3, and re-bleed. I think you'll find the leaks go away.
I these bikes newer is not always better.

[natemoen]

Dot 3 and 4 are compatible and can be mixed. As to the synthetic kind, that could be the problem, might be slipperier and able to leak past the old wore tolerances.

[XS1100_OEM4ME]

Synthetic?

OK, I will change back to DOT3? I do see that is what the cap says, but that was the best availabule in 1979. My understanding is that 4 absorbs / draws in less water and has a higher boiling point then 3 and the synthetic states it is compatibule with all dot 3 and 4 break fluids, both synthetic and standard but has an even higher boiling point, better corrosion protection and water resistants, so I was guessing it can't hurt and should help

[cywelchjr]

DOT 4 shouldn't have any affect like that. Unlike oils the brake fluid behaves pretty much like the standard stuff other than the higher boiling point and attracting less water part. It shouldn't affect the rubber parts any different and shouldn't slip by any rubber parts. Frankly I don't remember, but I THINK I put DOT 4 in mine last time (but I don't remember, I tend to just grab the first stuff that's on my shelf). The only place I've seen synthetics appear to be an issue on our machines is in the crankcase, primarily with the clutch, everywhere else they seem to work fine, I think the only place I DON'T have synthetic may be the crankcase and maybe the brake system (and it's the brake system I'm not sure about).

[XS1100_OEM4ME]

Non Synthetic?

OK, I see different opinions on this fluid thing, but I am willing to try anything before I spend the $$$$ on a new master cyl (I think mine sold for $100.00) So I goes to the auto parts store and look all over for #3 non synthetic brake fluid, DONT EXIST I found #3 and #4 and #3-4 and #5 and #5.1 ALL ARE SYNTHETIC Where do you guys get non synthetic brake fluid? Went on line, ALL SYNTHETIC, also, so I bought the cheapest #3 they had and it was SYNTHETIC Do you guys think that the # is causing the leak, or the synthtic thing

[cywelchjr]

I'd have to look at my bottle (if I can find it) but I think all the stuff you can buy now (and for the last few years as well) is/has been synthetic. So I think the synthetic thing is a non issue. There has got to be something else going on, maybe an o-ring that's not included in the kit or something that's leaking? I don't have any breakdowns here in front of me or such, but I can't think of any other reason for leakage.

[petejw]

did u coat the seals/bore with brake fluid/
rubber grease or did u put them in dry? jat

[XS1100_OEM4ME]

Exploded view.

OK, here is an exploded view of the M/C. Now before anyone says " its the "U" shaped washer or the "thingy betwen the main plunger and the piston" rembember, it worked fine for years with out those parts So, I am asking, to anyone who KNOWS, are those parts there in yours I took the greatest care to keep all parts in order as they came out of the M/C and replaced ALL parts that came in the K&L kit. There IS a washer, as shown in the pic (round, and the right size to hold in the plunger with the snap ring) There was no "thingy" between the plunger and the main cup (there were both of these on my rear M/C, but no "round washer to take the place of the "U" washer so I am thinking the pic is mixing the two M/C parts If you have a front M.C apart, and it has the "U" washer and the round washer and the "thingy between the cup and piston, PLEASE LET ME KNOW IT IS SUPPOSED TO BE THERE, THANKS. Dont know how it worked for years without it, but if I need it, but, oh well, just one more PO prob

http://www.boats.net/parts/search/Ya...OSE/parts.html

[tom clisham]

dot3 fluid

Walmart has dot 3 brake fluid

[XS1100_OEM4ME]

Ok


Non synthetic?? If so, the got the markrt cornered

Walmart has dot 3 brake fluid

[trdriver71]

I got my dot 3 non synthetic brake fluid at wal mart. It was the only place i could find it.

[XS1100_OEM4ME]

So

So, and I do thank you guys for the input, the non synthetic DOT3, with lower boiling point, no rubber part lube / conditioner or anti-corrsive additives, higher mosture attracting Fluid some way works better